Zoonoses: Diseases from Animals

Humans share the amazingly diverse world with an enormous variety of animals. Just like humans, animals can carry illnesses and sometimes they pass these illnesses on not just to others of their kind but to other types of animals as well--like humans. One of the standards listed in Caring for Our Children is that children wash their hands thoroughly after handling any animals, or feeding and caring for the center or family pet. The reason is "zoonoses."

Zoonoses (plural) and zoonosis (singular) are funny looking words. Pronounced "zoh-oh-noses," zoonoses means diseases of animals that can be transmitted to people--including those in childcare. Children may be exposed to animals in the childcare program or at a petting zoo, or may have pets at home. Children may enter a childcare program with a zoonotic disease so it is helpful to understand what they are. There are dozens of these diseases but this article focuses on some of the most important.

Animal Bites

The first of these diseases that comes to mind is the dreaded rabies, a fatal disease unless treated early, before symptoms appear. Although dogs used to be the main source of infections in humans, this is no longer the case, as a result of the almost universal practice of giving rabies shots to our dogs. It is just as important to protect cats against rabies as it is dogs.

Because public health agencies have nearly eliminated rabies in domestic animals, the threat of rabid animals now chiefly exists among those in the wild--raccoons, foxes, and skunks, in particular. Rabid animals often act unusually tame.

Bats are what is termed a "reservoir" of infection because they keep infection for extremely long periods of time. Although this is of particular concern to people who investigate caves, it also can involve children. A curious child might pick up a dead or sick bat on the playground, and if the bat is found to have rabies, the child must immediately begin a series of five rabies injections, the treatment for exposure to rabies.

Any animal bite, whether by a dog, cat, hamster, or a wild animal, should be reported to a doctor or to public health officials immediately. Rabies is not the only reason to be concerned about animal bites. It is estimated that about a million bites occur every year, half of them in children. Bites by cats and dogs frequently result in infections; infection is slightly more likely from cat bites than dog bites. This is because cat bites usually are puncture wounds that can allow dangerous organisms to thrive because they are not exposed to air. Dog bites, which are often more slashing or tearing, are somewhat less likely to become seriously infected. For both types of bites, it is important that the bitten child or adult be current with tetanus immunizations.

Catscratch Disease

Catscratch disease is transmitted by the scratch of a cat. The signs of catscratch disease in humans are swollen, tender, lymph nodes between the location of the scratch and the person's heart, in other words, in the lymph nodes that drain the part of the body with the scratch. A scratch on the hand or arm will cause swelling of the lymph nodes in the armpit on that side; an infected scratch in the foot or leg will produce swollen and tender nodes in the groin. There also may be fever. The catscratch itself usually is inconspicuous.

Treatment is with antibiotics, but only a few are effective against this germ. With or without antibiotics the infection gradually subsides. Catscratch disease is not contagious from one person to another.

Toxocara

Toxocara is a strange infection caused by a tiny one-cell microscopic organism that infects cats. The cats are not sickened by having toxoplasma in their bodies, so the toxoplasma organisms thrive in them. Toxoplasma eggs are found in cats' bowel movements. As the feces dries in the litter box, some of the eggs are dislodged as dust, and humans can become infected by inhaling dust while changing the litter box.

For most people, toxoplasma is fairly harmless. However, it is quite serious for the unborn child. If a pregnant woman gets toxoplasma, the tiny one-celled organisms can cross the placenta and invade the developing fetus. The germs seem to be particularly attracted to the baby's brain and, if they lodge there, can cause serious problems including mental retardation and visual problems. Although toxoplasma infection can be acquired in other ways, such as a cat bite, pregnant women should not empty cat litter boxes!

Salmonella

Salmonella is a major infection that occurs in poultry, livestock, and many other animals. For unknown reasons, turtles are particularly likely to be infected. Studies have shown that the majority of the imported funny little turtles have salmonellosis, and the federal government has banned their interstate shipment.

Salmonella is very common in petting zoos where it is easily transmitted to small hands. Careful handwashing, along with no thumb sucking, should be the rule for field trips to the petting zoos.

Other Diseases

Pinworms have the reputation of being a zoonosis, but they actually are not. Dogs have dog pinworms, cats have cat pinworms, and neither type can live long in people.

Ringworm is a pesky but not dreadful skin condition that can be acquired from pets. This is a fungus, not a worm at all. The pets should be treated by the veterinarian while the human is taken to a people doctor. Treatment is with a fungus-killing medicine. The medicine can be in taken in tablet or liquid form by mouth or as a cream applied directly to the affected area.

Scabies exists in different forms-dog scabies (called mange), cat scabies, and human scabies. Scabies acquired from a dog with mange can cause human skin problems on a temporary basis. It can be treated, but lasts only several days. Human scabies is caused by a mite, a very tiny eight-legged creature that irritates the skin by burrowing in it, just barely beneath the skin's surface. Human scabies is highly contagious. Itching is severe. Treatment comes from creams which are applied, usually in a head-to-toe fashion, and left on for a specified period of time. One treatment is usually enough.

Clothing that has been worn by a person infected with scabies should be washed or dry cleaned. If neither of these is possible, sealing the clothing (or other object) in a plastic bag for a week will be adequate. The mites cannot live more than a few days without a "skin meal."

Donald Palmer, MD
Chairman of the Child Care Committee, Alabama Chapter, American Academy of Pediatrics

Information on all of these diseases can be found at medlineplus.gov. Enter in the disease name in the search engine.

www.tdh.texas.gov/zoonosis/

www.mehtachildcare.com/misc/pets.htm

www.drlarrypetvet.com/health_zoonosis.html

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